Fluctuations of monsoon activity

Abstract

 In order to study the evolution of flow patterns associated with 'strong' and 'break' monsoon we have studied six cases each of such epochs during the period 1965 to 1973. As we are interested in the departure of the flow patterns from the normal, we have subtracted long term climatological pentad means from the daily data and constructed anomaly wind, height and thickness charts at standard levels.

The several contrasting features during the epochs as well as prior to the epochs. A few  days prior to the beginning  of the strong monsoon epoch (usually in association with a depression), an eastwest anomaly trough is seen extending from SE Asia to peninsular India in the lower and, middle tropospheres. The trough over peninsular India shifts northwards with the advance of the epoch. Westward movement of  a cyclonic anomaly from across Southeast Asia IS also seen. In the upper troposphere a warm anomaly ridge isseen to the northwest of India.

Prior to the beginning of breaks, however, an anomaly ridge is seen extending from peninsular India to Malaysia in the lower and middle tropospheres. This feature also shows some northward shift with the advance of the epoch. In the upper troposphere, an anomaly trough is seen to the northwest of India.